Modern cordless telephone systems provide for multiple handsets operating in conjunction with a single base station. The base station couples to a wire line telephone network. The base station also includes radio circuitry for communicating with the cordless handsets. The handsets include similar radio circuitry for communicating with the base station. Examples of such cordless telephone systems are systems operated according to the Digital European Cordless Telephone (DECT) standard, or systems operated according to the Personal Handy Phone system (PHS) in Japan.
Such systems provide numerous user convenience features which make use of this multiple handset capability. For example, the system supports calling from handset to handset, or call transfer between handsets, or paging between handsets, or handset-to-handset intercom features. These features are implemented using the base station as a common communication link, or may be implemented using direct communication between handsets. These features are available in systems in which the base station may be used as a hands free speakerphone or includes a corded handset for communication between the base station and a handset.
One problem occurring when using these user convenience features is the inability to know what other users or handsets are actively registered with the base. For example, a user answering an incoming call needs to know if the user for whom the call is intended is actively available in the system before transferring the call. Similarly, before intercom operation, a user would like to first determine if the other user is actively registered. However, current cordless telephone systems lack such capability.
Accordingly, there is a need in the art for a cordless telephone system which permits identification of active handsets prior to communication between handsets or communication between a handset and the base station.